Radiopharmaceuticals and lasers produce sound to treat and detect cancerous moles

Mar 1 2005

When treating skin cancer, differentiating between melanoma and healthy moles can be difficult. Doctors must know the shape of the cancer and how deep it is before treating the problem. Now, a skin care specialist at the University of Missouri-Columbia has teamed with MU engineering and internal medicine professors to develop a better identification and treatment process.

"The incidence and mortality rates associated with melanoma have increased as much as 7 percent in recent years," said Yubin Miao, a research assistant professor in internal medicine. "Early melanoma tumor diagnosis and prompt surgical removal are a patient's best hope for a cure. Unfortunately, metastatic melanoma is resistant to current chemotherapy and immunotherapy regimens."

Currently, technology can make identification of melanoma difficult. To treat the affected areas on the skin, doctors must know what areas are dangerous and, at the same time, identify healthy cells, which they avoid during the treatment. Miao is using radiopharmaceuticals, while his colleagues investigate the lasers that produce sound, to treat and detect cancerous moles.

Using diagnostic and therapeutic elements such as technetium-99m and rhenium-188, Miao is attempting to target receptors on the over-expressed cells of cancerous moles. He uses the technetium to visualize the melanoma and the rhenium to treat it. Since the therapeutic radiopharmaceuticals will be delivered selectively to the melanoma cells, the radiation dose to normal tissues and organs will be minimal.

"Using a drug that would only identify deadly moles would help us immensely," said Jon Dyer, assistant professor of dermatology. "Nearly 60,000 people each year develop melanoma. The earlier we detect it the better a survival rate. A detection tool that is specific and accurate will help us fight this very dangerous problem much more efficiently."

Once an abnormal mole or cancer is detected, the next step is to create a detailed picture of the cancer site. John Viator, an assistant professor of biological engineering, is employing lasers to generate a high-resolution picture of the affected area through photoacoustics, which is a laser-induced ultrasound, but much more detailed. While ultrasound generates sound waves and listens to the echoes to create grainy pictures, Viator uses low-energy lasers to target blood vessels, creating a sound wave inside the body. A special listening device then detects these sounds and creates a detailed picture on a computer. While an ultrasound's resolution is about one millimeter, the laser may create a resolution of about 10 microns.

One difference between using the laser instead of the ultrasound is that the laser can only penetrate the skin by a few millimeters. Though laser-induced ultrasound is not suitable for imaging deep organs, it is ideal for creating highly detailed pictures of the skin's structure. These detailed pictures can show skin specialists the exact size and shape of the dangerous skin cells and how far they penetrate. Specialists such as Dyer can then pinpoint therapeutic strategies to destroy the bad skin cells without ever touching the healthy cells.

"This research opens myriad possibilities," Dyer said. "Currently, when we want to rid the skin of a dangerous birthmark or mole, we destroy the blood vessels in the area, but too much heat can destroy melanin and healthy skin cells. With the new technology, we will be able to target individual cells, thus reducing the damage to healthy tissue but increasing our accuracy to destroy the cancer."

Dyer said that skin specialists also will be able to treat non-cancerous marks on the skin that are a result of capillary malformations, typically called port wine stains. While they do not carry a risk of developing into a cancer, these port wine stains can be a burden cosmetically. Using photoacoustics, doctors could characterize the moles better and have a better success rate in treating the marks.

The researchers expect to begin using the technology in clinical applications within the next two years. A pilot study has been scheduled for this summer.

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